Electrolytic apparatus and method



March 2, 1937.

J T. ELLSWORTH ELECTROLYTIC APPARATUS AND- METHOD Filed July 11, 1935 2 Sheets-Sheet 1 March 2, 1)37. J.T. ELLSWORTH ELECTROLYTIC APPARATUS AND METHOD Filed July 11, 1935 2 Sheets-Sheet 2 13209223031- J'OM 1 1177451008 3? yfl m V Patented Mar. 2, 1937 ELECTROLYTIC APPARATUS AND METRO John '1. Ellsworth, @gden, Utah, assignor to Industrial Development (Jorporation, Boston, Mass., a, corporation of Maine Application July 11, 1935, serial No. 30,871

12 @iaims.

This application is a continuation in part of application Serial No. 552,141, filed July 21, 1931.

My invention relates to electrolytic apparatus and methods, and more particularly, but not exclusively, to methods of and apparatus for producing electro-deposited metallic sheets, with provision for controlling and replenishing the metal content of the electrolyte.

The invention will be best understood from the following descriptions of several examples of the practice of a method according to theinvention, and of one embodiment of apparatus for use in practising the method, the scope of which invention will be more particularly pointed out in the 1' appended claims;

In the drawings:- Figure 1 is a schematic diagram of one form of apparatus for use in the practice ofthe im- -proved method; Fig. 2 is an elevation, with parts broken away and parts in section, of an electrolytic cell constructed according to the invention, this figure corresponding to a section ,on the line 2-2 of Fig. 3;and

Fig. 3 is a sectiori on the line 3-3 of Fig. 2. The electrolytic cell illustrated in the drawings is more particularly described in United States Patent No. 1,993,726, issued March 5, 1935 on an invention by Richard A. Wilkins, and, in respect to common subject matter, does not form part of applicants invention.

As shown, the cell comprises a suitably supported trough I, which preferably is of sheet lead and which herein constitutes an insoluble anode. R0- tatably mounted in the trough is a drum 3, which herein constitutes a cathode, the drum having a shaft 5 which is provided with a driving sprocketwheel I for a chain (not'shown), and is rotatably supported in bearings 9. As shown, the lower 40 portion of the trough is arcuate, and has its interior surface concentric with the adjacent surface of the drum in relatively closely spaced relation thereto. Electrolyte is supplied the cell from a conduit II, which delivers the electrolyte to a fore-bay l3 at the left handend of the trough, as viewed in Fig. 2. The electrolyte accumulates in the fore-bay and a minor portion thereof, say 10%,,is-permitted to overflow weir I5, thus establishing a substantially constant hydraulic head on the opening "i at the bottom of the weir through which the major portion of the electrolyte is discharged. The fore-bay provides for accumulation of a large body of electrolyte from 1 which entrapped air may escape before the'electrolyte passes to the cell and for providing a head whichimpresses on the electrolyte entering the cell the necessary velocity, causing it to pass by the cathode in a relatively swiftly flowing stream. At the right hand end of the trough, as viewed in Fig. 2, is an undercut weir II, a small portion of the electrolyte discharging overthe top of-the weir and the major portion thereof flowing through the orifice l9 beneath the weir, so as to maintain the electrolyte-level indicated at 2| substantially horizontal. The electrolyte which passes the weir I'I falls into a chamber 23 from which it is discharged through a conduit 25 schematically indicated in Fig. 1.

As shown in Figs. 2 and 3, a sheet 21, electrodeposited from the electrolyte, is stripped from the unsubmerged upper portion of the cathode drum at the side of the latter where the cathode one-tenth of one foot per minute. Applicant has i found that if electrolyte is permitted to splash on the unsubmerged surface of the cathode, the drops of electrolyte upon drying will form small crystals of the metal salt which is in solution in the electrolyte, as'for example, when copper is being electro-deposited, small crystals of copper sulphate. These crystals act to cause the electrodeposited sheet to be pitted, and to cause perforations therein, which pits and perforations for many uses of the sheet material are objectionable. In the present embodiment of the invention, it will be observed that the sheet being stripped from'the right hand side of the cathode, as viewed in Fig. 3, protects the portion of the cathode surface above said sheet from the electrolyte that would otherwise be splashed upon it. For preventing electrolyte being splashed upon the cathode surface at the left hand side thereof, as viewed in. Fig. 3, herein is shown a splash plate 33, preferably formed of rubber or other non-conductive material, this splash plate preferably being positioned close to the electrolytelevel, and substantially closing the space between the cathode surface and the adjacent wall 35 of the trough l, upon which wall it is supported by suitable spaced brackets 31.

Applicant has found that when electro-depositing by the use of the .cell above described, the metal content of the electrolyte may be readily replenished by passing it in contact with metal bearing material, as for example, when copper is being electro-deposited, passing it .in contact with copper scrap, or when zinc is being deposited, passing it. in contact with zinc scrap, and that this replenishment is greatly facilitated by the sludge which forms in the electrolyte, it being understood that copper and zinc are not otherwise readily soluble in dilute sulphuric acid. Applicant, as explaining the action of the sludge in producing this phenomenon, advances the theory that sludge acts in the nature of a catalyst, that is to say, an oxygen carrying medium which in a sense activatesthe dilute acid to cause it to dissolve the copper or zinc toproduce copper sulphate or zinc sulphate, the most active catalyst in the sludge possibly being lead peroxide (PbOz) produced in the cell by the action of the electrolytically decomposed electrolyte on the lead anode.

Applicant has further found that the presence of sludge in the electrolyte supplied the cell produces a more or less roughened surface on the electro-deposited sheet, and that a sheet with a. smooth. surface may be produced by causing the electrolyte supplied the cell to be free from sludge.

The present invention contemplates, among other things, passing a sludge-free .fraction of the, electrolyte through the cell, and replenishing the electrolyte by causing another fraction, charged with sludge, to flow in contact with the body of metal bearing material, the two fractions being mixed after one discharges from the cell and the other from the container or the likehavingthe metal bearing material, after which the electrolyte is again divided into two fractions, one sludge-free and the other charged with sludge, and the operation continuously retaining the metal content of the electrolyte between predetermined limits by regulating the fraction thereof which; charged with sludge, contacts with the metal bearing material.

Referring particularly to Fig. 1, the supply conduits, ii for the several cells are shown as communicating with a common supply duct 30 which receives electrolyte from a reservoir 4i.

As illustrated, electrolwe is discharged into the right hand side of the reservoir from a conduit 03, this side of the reservoir being divided from the left hand side, with which latter the duct 39 communicates, by a filter partition 65, so that the electrolyte supplied the duct 30 will be free from sludge. From the lower portion of the right hand side'of the reservoir, a fraction of the electrolyte, as shown,'is discharged through a conduit 5'! into a vat 09 containing the metal bearing material, whence this fraction of the electrolyte, after replenishment, discharges through a conduit 5! into an electrolyte collecting tank 53, from which latter it is forced by a pump 55 into the conduit 43 to raise it to the reservoir M, The discharge conduits 25 for the several cells are shown as communicating with a common duct 51 which. 'also discharges into the electrolyte collecting tank 53, as does also the overflow conduit 59 from the reservoir M. As illustrated, the three conduits or ducts 5H, 51 and 59 have their discharge ends close together at the end of the collecting tank,53 remote from the pump 55, which facilitates mixing of the various supplies from these, sources. In the apparatus indicated by Fig. 1, the conduit 41 is 75 provided with a valve 6!, and each supply conpeated. The invention also contemplates main-' duit H for the several cells with a valve 63,-

by use of which valves a constant flow of electrolyte 'may be maintained through the cells, and a regulated fraction maintained through the conduit 47, the excess electrolyte discharging from the reservoir 4i into the conduit 59. By controlling the amount of electrolyteflowing through the conduit 41, it will be observed that the rate of replenishment of the electrolyte supplied the cells may be controlled. Conveniently,

the electrolyte may be aerated by so arranging the various conduits that the electrolyte discharging therefrom falls through the air for a short distance.

As illustrated, the vet '09 is provided with staggered bames 65 and Bi to form compartments which contain the electrolyte replenishing metal. As shown, the battles 65 do not extend entirely to the bottom 69 of the vat, and provide more or less restricted orifices H through which the electrolyte flows, the restriction of these orifices preferably being such as-to cause an eddying action of the electrolyte to maintain the sludge in suspension and to maintain it in intimate contact with the metal bearing material. The metal bearing material in the tank may-be of any suitable form, as for example, may be a matted mass of copper wire scrap indicated at 73, or may be in the form of broken up pieces of copper or zinc scrap, blister copper shot, zinc sprouts, or calcined jig or flotation copper or zinc concentrate, supported on perforated trays 15 or, as indicated at Tl, placed in .the bottom of the compartments.

Applicant has found that the replenishing action is facilitated by heating the electrolyte, as for example, by use of a. steam coil 19 placed at the inlet end of the vat 09. It has been found that best results will be secured by maintaining the electrolyte at temperatures in excess of F., 120 F. being a satisfactory temperature in th practical operation of the apparatus.

As. an example of the practice of the invention, but without limitation thereto, it has been found that satisfactory results may be obtained with cathodes about 24 inches in diameter and 60 inches long, with the arcuate portion of the insoluble anode trough corresponding to about 120 of circumference of the cathode surface and spaced therefrom about five-eighths of an inch, and with a total voltage impressed on each cell roughly about 3 volts for copper and 4.5 volts for zinc, whenabout gallons of electrolyte per minute are passed through each 'cell and 5 gallons per minute per cell through the electrolyte replenishing vat, with the, temperature of the electrolyte in said vat being about F. Under these conditions satisfactory results are secured when depositing copper by maintaining the electrolyte at about 9 ounces of copper per gallon in the form of copper sulphate, with about 10 ounces of sulphuric acid per gallon, the sheet copper produced being about 0.005 of an inch thick. When depositing zinc the electrolyte may be maintained at about 12 ounces of zinc per gallon in the form of zinc sulphate, with about 13 ounces of sulphuric acid per gallon, the zinc sheet produced being about 0.005 of an inch thick.

In operating the apparatus, if desired, the metal content of the electrolyte may be maintained between convenient upper and lower specific gravity limits, as for example, when depositing copper between 1.18 and 1.24, the former of which corresponds to approximately 26 ounces of copper sulphate crystals per gallon and 10% sulphuric acid the latter corresponding to approximately 59- ounces of zinc sulphate crystals per gallon and 6% sulphuric acid concentration.

It will be understood that if sludge from other cells is not available in initiating operation of the apparatus the electrolyte may be replenished with copper or zinc sulphate until the sludge builds up in amount suilicient to supply the needs of the apparatus.

It will be understood that within the spirit of v the invention wide deviations may be made from the form of the apparatus and product and way of practising the method herein described.

I claim: l. The method of replenishing the metal content of an acid metal sulphate electrolyte of the group comprising copper sulphate and zinc sulphate which comprises treating copper or zinc bearing material respectively with the electrolyte and *with sludge formed in an electrolytic cell having a cathode, a lead anode and an acid metal sulphate electrolyte, and causing said sludge to be in suspension inthe electrolyte which treats said material and such electrolyte intimately to contact with said material for dissolving-metal into the electrolyte.

2. The method of forming electro-deposits of metal of the group comprising copper and zinc from copper or 'zinc bearing material respectively which comprises supplying an acid sulphate elec- 40 trolyte of the metal, free from sludge, to an electrolytic cell having a cathode and a lead anode. passing the electrolyte through said cell in a stream of sufiicient velocity to carry away from said cell sludge formed therein, and replenishing the metal content of the electrolyte discharged from said cell by causing sludge removed from said cell to be in suspension in the electrolyte and causing the electrolyte containing the suspended sludge intimately to contact with said metal bear- 7 ing material for dissolving metal into the electrolyte. I

3. The method of forming electro-deposits of metal of the group comprising copper and zinc which comprises treating copper or zinc bearing material respectively with an acid sulphate electrolyte of the metal, freeing from. sludge electrolyte which has treated said material, electrodepositing metal from the sludge-free electrolyte in an electrolytic cell having a cathode and a lead anode, supplying sludge formed in said cell to the electrolyte which treats the metal bearing material. and causing the sludge to be in suspension in the electrolyte as said material is treated thereby and the electrolyte intimately to contact with said material for dissolving metal into the electrolyte.

4. The method of replenishing the metal content of an acid metal sulphate electrolyte of the 70 group comprising copper sulphate and zinc sulphate which comprises suspending in the electrolyte sludge formed in an electrolytic cell having a cathode, a lead anode and an acid sulphate electrolyte of the metal, and causing the electro- 75 lyte containing the suspended sludge intimately to contact with metal bearing material ior dissolving such metal into the-electrolyte.

5. The method of forming electro-deposits of metaloi the group comprising copper and zinc from copper or zinc bearing material respectively which comprises passing an acid sulphate electrolyte oi. the metal through an electrolytic cell having a cathode and a lead anode, leaching said material with an acid sulphate electrolyte of the metal, mixing lean electrolyte discharged from said cell with electrolyte which has leached said material, separating sludge from the electrolyte which has been discharged from said cell, and confining the separated sludge to the electrolyte which leaches said material whereby the electrolyte supplied said cell is sludge-free and .said material is leached by an electrolyte which contains sludge.

6. The method of forming electro-deposits of metal of the group comprising copper and zinc from copper or zinc bearing material respectively which comprises passing an acid sulphate electrolyte of the metal through an electrolytic cell having a cathode and a lead anode, leaching said material with an acid sulphate electrolyte of the metal, mixing lean electrolyte discharged from said cell with electrolyte which has leached trolyte which has been'discharged from said cell, confining the separated sludge to the electrolyte which leaches said material whereby the electrolyte supplied said cell is sludge-free and said material is leached by an electrolyte which contains sludge, and regulating the metal content of the electrolyte supplied said cell by varying the amount of electrolyte which leaches said material.

'7. The method of forming electro-deposits of metal of the group comprising copper and zinc from copper or zinc bearing material respectively which comprises subjecting to the action of said material an acid sulphate electrolyte of the metal containing sludge formed in an electrolytic cell during metal deposition in the presence of a lead anode, supplying a sludge-free acid sulphate electrolyte of the metal to an electrolytic cell having a cathode and a lead anode and passing such electrolyte through said cell in contact with said anode and cathode, mixing electrolyte discharged from said cell with electrolyte which has been subjected to the action a said material, separating sludge from the elecof saidmaterial, and separating said mixed electrolyte into two fractions one of which is sludgefree for return to said cell and the other of which contains sludge for subjection to the action of said material.

8. The method of forming electro-deposits of metal of the group comprising copper and zinc from copper or zinc bearing material respectively which comprises subjecting to. the action of said material an acid sulphate electrolyte of the metal containing sludge formed in an electrolytic cell during metal deposition in the presence of a lead anode, supplying a sludge-free acid sulphate electrolyte of the metal to an electrolytic cell having a cathode and a lead anode and passing s'uch electrolyte through said cell in contact with said anode and cathode, mixing electrolyte discharged from said cell with electrolyte which has been subjected to the action of said material, separating said mixed electrolyte into two freetions one of which is sludge-free for return to said cell and the other of which contains sludge for subjection to the action'of said material, and regulating the metal content of the electrolyte supplied said cell by varying the amount of sludge containing electrolyte subjected to the action of said material.

9. The method of forming electro-deposits metal of the group comprising copper and zinc from copper or zinc bearing material respectively which comprises subjecting'to the action of said material an acid sulphate electrolyte oi the metal containing sludge formed in an electrolytic cell during metal deposition in the presence of a lead anode, supplying a sludge-free acid sulphate electrolyte of .the metal to an electrolytic cell having a cathode and a lead anode and passing -separating sludge from said electrolyte, means including electrolyte conveying conduits for passing a part of said electrolyte through said cell between said anode and cathode in contact therewith and for causing another part to contact with said metal bearing material, means for mixing electrolyte discharged from said cell with electrolyte discharged from in contact with said metal bearing material, and means including said conduits for subjecting the mixed electrolyte to the action of said means for separating sludge for freeing a portion thereof from sludge and tor supplying said cell with electrolyte from such sludge-free portion of the mixed electrolyte and for causing electrolyte mixed with sludge from the remaining portion to contact with said metal bearing material.

11. Apparatus for electro-deposition oi metal comprising a cathode, a lead anode in proximity to saidcathode, a body of metal bearing material, a body of metal sulphate electrolyte; means for passing a part of said body of electrolyte through said cell in contact with said anode and cathode, and separate means for subjecting another part of said body to the action of said material; means for mixing electrolyte discharged from said cell with electrolyte which has been subjected to the action of said material, and. for causing a fraction of the mixed electrolyte to be supplied said cell; and means including a sludge separator for causing the electrolyte supplied said cell to be free from sludge and the sludge in the electrolyte discharged from said cell to be mixed with the electrolyte subjected to the action of said body.

12. The method otproducing electro-deposited metal of the group comprising copper and zinc from copper or zinc bearing material respectively which comprises flowing an acid sulphate electrolyte of the metal through an electrolytic cell having a cathode and a lead anode, in which cell the electrolyte contacts with said cathode and anode, flowing electrolyte in contactwith the metal bearing material, mixing electrolyte discharged from said cell with electrolyte discharged from in contact with said material, and transferrin the sludge formed in said cell from the electrolyte discharged from said cell to electrolyte which flows in contact with said metal bearing material.

JOHN '1. ELLSWORTH. 

